The present invention relates to a fluid coupling and more particularly a fluid coupling which transmits power between a power input shaft and a power output shaft. The fluid coupling of the present invention has particular utility in automotive vehicles and machine tool drive mechanisms or any other installation requiring power transmissions.
Fluid couplings per se are known in the art and have been extensively used in power transmissions. A typical coupling device is disclosed in U.S. Pat. No. 1,954,418 wherein the discharge valving of the device is manually controlled. When the discharge ports are uncovered no power is transmitted from the drive member to the driven member. As the valve is moved so as to throttle the discharge ports power is transmitted from the drive member to the driven member. When the valve completely covers the discharge ports the drive and driven members rotate in unison in 1:1 ratio.
U.S. Pat. No. 3,696,896 discloses a fluid coupling having centrifugally actuated valving for controlling the discharge ports. Such a device suffers from the disadvantage that the drive and driven members are locked in 1:1 ratio at a specific RPM of the drive member. Thus, at a RPM less than the specific lock up RPM the relative movement between the drive and driven members would result in heat build up and wear thereby adding to servicing costs of the device. In addition to the foregoing, upon deceleration, the device would freewheel thereby offering no braking action.
In order to overcome the aforenoted disadvantages, it would be highly desirable to design a fluid coupling in which the lock up RPM between the drive and driven members is variable depending on the torque or power applied to the drive member. By providing such a device, at ordinarily operating ranges of speed the unit will be locked in 1:1 ratio thereby minimizing wear and heat build up and correspondingly servicing costs.
Accordingly, it is the principal object of the present invention to provide a fluid coupling device which is of simple construction and less complex than automatic transmissions known in the art.
It is a particular object of the present invention to provide an improved fluid coupling device in which the lock up RPM between the drive member and the driven member is variable depending on the torque and RPM applied to the drive member.
It is a still further object of the present invention to provide an improved fluid coupling device in which freewheeling is eliminated upon deceleration of the device.
Further objects and advantages of the present invention will appear hereinbelow.